1. Field of the Invention
The present invention relates to a wireless local area network system, and more particularly, to a method of communication for station operating based on battery in a wireless local area network system and apparatus for the same.
2. Related Art
With the advancement of information communication technologies, various wireless communication technologies have recently been developed. Among the wireless communication technologies, a wireless local area network (WLAN) is a technology whereby Internet access is possible in a wireless fashion in homes or businesses or in a region providing a specific service by using a portable terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), etc.
The IEEE 802.11n is a technical standard relatively recently introduced to overcome a limited data rate which has been considered as a drawback in the WLAN. The IEEE 802.11n is devised to increase network speed and reliability and to extend an operational distance of a wireless network. More specifically, the IEEE 802.11n supports a high throughput (HT), i.e., a data processing rate of up to above 540 Mbps, and is based on a multiple input and multiple output (MIMO) technique which uses multiple antennas in both a transmitter and a receiver to minimize a transmission error and to optimize a data rate.
Wireless LAN systems support active mode and power save mode as an operation mode for stations STAs. In the active mode, STAs operate in an awake state to transmit and receive frames. A power save mode is supported for power saving of STAs which need not remain in the active state for frame reception. STAs which back up PSM operate in a doze mode to prevent unnecessary power consumption while the STAs cannot access the wireless medium. In other words, the STAs operate in the awake state only while the STAs can transmit or receive frames.
As WLAN systems are widespread, a single AP (Access Point) provides services to many non-AP STSs. Further, as the number of mobile-type non-AP STAs which support WLAN increases, methods are required that can support increased mobility.
An M2M (Machine to Machine) network is an example of an environment where multiple STAs are present in a single wireless LAN system. In the existing WLAN systems, a human approaches an AP through a non-AP STA to receive services. In the M2M network, however, a machine which supports WLAN communication plays a leading role to transmit and receive information.
In the existing WLAN systems, a non-AP STA used by a user requests information via an AP and receives information from the AP. In a general WLAN system, processes for link establishment, such as scanning, authentication, and association, are actively performed through a request from the non-AP STA. This is appropriate for a communication flow in which a user requests information through a non-AP STA and obtains requested information from an AP. In contrast, in an M2M-supported WLAN system, a user requests through an AP that a plurality of non-AP STAs associated with the AP send information and obtains information from each non-AP STA.
As such, introduction of M2M-supported WLAN systems and increased mobility of STAs may be incorporated with battery-based operation. Accordingly, power management of STAs becomes more crucial. Thus, there is a need for a communication method for battery-based STAs and a device of supporting the method, which can effectively apply to the wireless LAN environment.